1. Field of Invention
The present invention relates to a near infrared (NIR) absorbing agent.
2. Description of Related Art
Tungsten bronzes MxWO3 (M=Li+, Na+, K+, Rb+, Cs+) are known to possess a satisfactory absorption of NIR light (having a wavelength between about 750 nm to about 1400 nm) while retaining a high transmittance of visible light (having a wavelength between about 380 nm to about 750 nm).
However, conventional methods for preparing tungsten bronze usually involve an annealing step at a temperature higher than 300° C. to produce the crystalline products that exhibit desirable NIR absorption. High temperature annealing would usually raise the manufacturing cost and is undesirable.